Falling film type heat exchanger



July 25, 1967 c. F. ROSENBLAD I 3,332,469

FALLING FILM TYPE HEAT EXCHANGER Filed Sept. 15, 1966 2 Sheets-Sheet 1 42 I m" Z4 '17 STEAM PL P3:

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CUR? EAQSENBLAD ATTORNEY United States Patent 3,332,469 FALLING FILM TYPE HEAT EXCHANGER Curt F. Rosenhlad, Rosenblad Corp, 19.0. Box 585, Princeton, NJ. 03540 Filed Sept. 13, 1966, Ser. No. 579,072 8 Claims. (31. 1sa 13 This application is a continuation-in-part of application Ser. No. 423,492, filed Ian. 5, 1965.

This invention relates to a plate type heat exchanger of the falling film type. More particularly, the invention relates to an improved liquid distribution device for such heat exchangers, the distribution device insuring the creation of substantially uniform falling films on the entire heating surfaces of the heat exchanger plates.

This invention and that of application Ser. No. 423,492 above referred to are improvements over those disclosed and claimed in application Ser. No. 303,824, filed Aug. 22, 1963, by the present applicant; Ser. No. 310,527, filed Sept. 23, 1963, by Axel E. Rosenblad; and Ser. No. 350,454, filed Mar. 9, 1964, by Elof M. Rosenblad, all of which are now abandoned. The three earliest filed of such prior applications disclose heat exchangers of the falling film type wherein liquid is distributed to the heating surfaces of the plates by means including spray nozzles or the like disposed within liquid medium receiving channels adjacent the top thereof. In all of such prior devices, if the films formed upon the heating surfaces are to be substantially uniformly distributed thereover, the spray or jet producing means must be located close to the heating surfaces. This leads to difficulty in maintaining the spray or jet producing openings clear and working at their maximum efiiciency, particularly when the liquid being heated and/ or evaporated carries a substantial amount of solid matter in particle form. The requirement of a small distance between the jet-forming means or nozzle and the heating surfaces entails frequent maintenance and cleaning of the apparatus if the films on the plates are to remain substantially uniform and to cover the full extents of the heating surfaces.

In accordance with the present invention, liquid to be heated and/or evaporated is introduced into the heat exchanger through one or more openings or nozzles disposed above the upper edges of the heat exchanger plates. The openings or nozzles are preferably disposed so as to be substantially uniformly distributed over a given zone or area of the upper ends of the plates. Interposed between such openings or nozzles and the upper entrance ends of the medium receiving channels of the heat exchanger is a novel bafiie or spray intercepting means of such construction as to prevent any substantial amount of the liquid falling from the openings or nozzles from directly impinging upon any of the heating surfaces of the plates, including the top portions thereof. Liquid intercepted by the upper portion of such baffle means falls downwardly therealong under the action of gravity and preferably falls upon a still further portion of the baffle means which leads it in the form of a falling film onto the upper edges of the heating surfaces of the plates over the entire lengths thereof.

The battle means in accordance with the invention is so made that it presents no narrow apertures or passages therethrough in which solid particles entrained in the liquid being distributed may catch. Consequently, heat exchangers provided with liquid distributing means in accordance with the invention may be run for long periods without the necessity of being cleaned.

In the preferred embodiments of the invention disclosed herein, the baflle means includes elongated upwardly convex hoods or baflle members, either solid or hollow, which are disposed along the upper edges of the heating channels of the heat exchanger. The baffle means 3,332,469 Patented July 25, 1967 includes at least one further set of generally similar upwardly convex hood or baffle members which are disposed bteween the first set of hood members so as to overlap the first hood or bafile members when viewed from the points of view of the respective liquid discharging openings or nozzles employed to supply liquid to a particular area of the heat exchanger plates. As above set forth, it is a prime requisite of the present invention that the baffie means functions to prevent direct impingement of any substantial amount of liquid from the liquid discharging openings or nozzles onto the heating surfaces of the heat exchanger.

It is accordingly among the objects of the present invention to provide a novel liquid distributing system for a falling film type heat exchanger.

A further object of the invention resides in the provision of a novel liquid distributing system of the type described which insures the formation of films of liquid of substantially uniform thickness which covers the entire heating areas of the plates of the heat exchanger.

Yet another object of the invention lies in the provision of a liquid distributing device for heat exchangers of the falling film type wherein the liquid conveying assages of the distributing device are of substantial Width and breadth whereby the device may pass liquid containing solid particles without becoming plugged thereby.

A still further object of the invention, in preferred embodiments thereof, lies in the provision of a liquid distributing device incorporating one or more liquid discharging openings or nozzles spaced above the plates of the heat exchanger and in combination therewith a novel bafile device which prevents direct impingement of any substantial amount of the liquid from the openings or nozzles onto the heating surfaces of the heat exchanger while forming the intercepted liquid into films of substantially uniform thickness and forwarding them to the upper edges of the plates over substantially the entire lengths thereof.

The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. 1 is a view in vertical section through a first illustrative embodiment of plate type heat exchanger provided with a first fluid distributing device in accordance with the invention, the section being taken transverse to the broad surfaces of the plates of the heat exchanger;

FIG. 2 is a view in vertical section through the heat exchanger of FIG. 1, the section being taken at right angles to the section of FIG. 1 and along the line 22 in FIG. 1 looking in the direction of the arrows;

FIG. 3 is a view in horizontal section through the heat exchanger shown in FIGS. 1 and 2, the section being taken along the line 3-3 of FIG. 1;

FIG. 4 is a fragmentary view in vertical section taken similarly to FIG. 1 of a portion of the liquid distributing device of the heat exchanger of FIGS. 1, 2, and 3; and

FIG. 5 is a fragmentary view taken in a manner similar to that of FIG. 4 of another embodiment of liquid distributing system in accordance with the invention.

As is apparent from the above, there are shown herein two embodiments of liquid distributing systems for falling film type heat exchangers in accordance with the invention: (1) the embodiment of FIGS. 1-4, inclusive, and (2) the embodiment of FIG. 5.

Turning now to the embodiment of heat exchanger shown in FIGS. 1-4, inclusive, such heat exchanger is generally designated by the reference character 10. The heat exchanger is generally in the form of a vertical column of rectangular horizontal section, the heat exchanger having an enclosure with a left-hand cover plate 11 (FIG. 1), and a right-hand cover plate 12, the vertical edges 14 and 15 of the covers extending outwardly to form flanges by means of which the cover plates, heat exchanger plates, and sealing and spacing bars between the edges of the plates are bolted together (FIG. 2). Vertically disposed within the enclosure in spaced parallel relationship and parallel to the cover plates 11 and 12 are a plurality of heat exchanger plates 16. Alternate successive pairs of plates are closed at their ends, tops, and bottoms to form a plurality of channels 17 which receive the fluid heating medium for the heat exchanger. The other set of channels, designated 19, are interposed between succes sive heating channels 17. Channels 19 are closed at their ends but are open at their tops and bottoms to receive medium to be heated and/or evaporated by the heat exchanger. As shown, the parallel spacing of the plates 16 is substantially maintained despite pressure differentials in the channels 17 and 19 by means of conventional spacer or distance studs 18, which are secured to one of each pair 'of confronting plates 16.

Heating medium such as steam is supplied to the channels 17 by a pipe 20 connected to a manifold 21 which spans and is connected to each of the heating channels 17 at the top thereof, as shown. Condensate from such heating medium is exhausted from the channels 17 through a manifold 23 which spans and is connected to the channels 17 at the bottoms thereof. The manifold is connected to a discharge pipe 22 through which the condensate is led to a sump or the like. Disposed as an extension above the main portion of the enclosure about the plates 16 is a header 24 which forms a compartment above the heating plates into which the liquid medium to be heated and/or evaporated by the heat exchanger is introduced. Such liquid, after having traveled in the form of films along the heating surfaces of plates 16 in channels 19, falls into a vapor body or lower compartment 25 to form a pool of liquid 26 such as a concentrated liquor therein. If the liquor 26 carries a considerable amount of vapor by reason of evaporation effected by the heat exchanger, a bafiie 27 is provided interiorally of enclosure 25 so as to separate vapors formed on the heating surfaces from the liquor and to discharge the vapors through a conduit 29 connected to the baffle.

In the illustrative embodiment the heat exchanger 10 is shown employed to concentrate waste sulphite pulpcooking liquor from a pulp-making operation. The concent-rated liquor 26 is discharged from the pool thereof through a conduit 28. A certain amount of the concentrated liquor is usually recirculated through the evaporator to produce the flow rate thereof which is required to cover the heating surfaces with falling films. This is accomplished by having the liquor pass downwardly through a discharge pipe 30 into a pump 31 which forwards it under pressure through a pipe 32 to a further manifold pipe 39. Pipe 39 supplies the spray nozzles 41 and 42 of the liquid distributing device of FIGS. 1-4, to be described. The liquor supplied to such nozzles is mixed with fresh dilute liquor fed through a pipe 34 which is connected to a valve 35 as shown in FIG. 2. Valve 35 is under the control of a conventional means 37 responsive to the level of concentrated liquor 26 in the vapor body. Device 37 with valve 35 causes the system to deliver a continuous flow of liquor to the evaporator, the evaporator in turn delivering liquor of a predetermined greater concentration, termed the product. The rate of flow of the product liquor is usually manually controlled by a valve (not shown) in the product line 28.

In the embodiment of FIGS. 1-4, inclusive, liquid to be heated and/or evaporated in the heat exchanger is introduced into the chamber 24 at the top thereof through a plurality of nozzles which create downwardly directed sprays. Three such nozzles are shown, the central nozzle being designated 41, and the two outer side nozzles being designated 42. Nozzles 41, 42 are disposed within a central extension 40 rising above the chamber closure 24. The nozzles are of such character and are so disposed that the sprays therefrom substantially uniformly cover the areas of the heat exchanger plates above which they are disposed while somewhat overlapping at the upper portion of the baffle means 59 to insure complete coverage of all of baffle means. The sprays from the nozzles 41, 42 are intercepted by a baffle means 45, to be described, the baffle means being such as to spread the sprayed liquid there-over and to lead it onto the upper edges of the main vertical portions of the heating plates 16.

Baffle means 45 are shown more particularly in FIG. 4. As there shown, the joints 46 between the upper edges of the plates 16 are in the form of tight, welded seams of substantial vertical extent lying horizontally centrally above the vertical central plane of the respective channel 17. Below the joints 46 the plates 16 incline upwardly symmetrically inwardly toward each other in generally fiat portion 51. The portions 51 of plates 16 and the joints 46 between the upper edges of the plates constitute first baffle members of the bafile means 45. Bafiie means 45 includes further, second bafile members 47, 48 of which each of members 47 is supported by a plurality (two shown) of bafile supporting means 52 which extend across the channels 19 and are supported upon the upper edges of the two confronting plates 16 which form the channels 17.

In the embodiment shown the baffles 47 are formed of bent sheet material such as metal and are in the form of broad inverted Vs extending parallel to the broad extents of the plates 16. The baffles 48' at the right and left-hand ends of the plate structure as shown in FIG. 1 are in the form of oppositely disposed vertically divided halves of the baffles 47. Each of the baffies 47, 48 has its upper apex edge 49 disposed substantially at the same level as the upper edges of the joints 46. The baffles 47 are symmetrically disposed above the channels 19 with the apex 49 of each baflie 47 lying on the vertical longitudinal midplane of the respective channels.

In the embodiment of FIGS. 1-4, inclusive, the lower edges 50 of the baffies 47, 48 lie substantially in vertical planes which are tangent to the outer surfaces of the main, broad extents of plates 16 defining the channels 19.

The baffles 47, 48 are supported on the plate structure by the above-mentioned supporting means 52 which is shown more particularly in FIGS. 3-5, inclusive. Each supporting means 52, which may be made of plate metal, is of generally T-shape, having a head portion 54 and a central vertical lower portion or leg 55 depending therefrom. The head portion 54 of supporting means 52 has a horizontal width which somewhat exceeds the distance between the vertical central planes of successive channels 17, so that the end portions of the head overlie the joints 46 at the upper edges of the plates 16. The lower edges of the ends of the head portion 54 are notched at 57, such notches receiving the respective joints 46. The leg 55 in its lower portion has a width which is substantially that of the channels 19. The notches 57 and the leg 55 of the supporting means 57 accurately locate such means with respect to the channel 19 with which it is associated. The head portion 54 of the supporting means is provided with a centrally disposed isoceles triangular hole 56, which is disposed with the apex of the triangle upwardly, so as to retain the bafile members 47 in the described position relative to the channels 19. As shown in FIG. 3, successive supporting means 52 in each row thereof are staggered to avoid interference between their end portions. The end baflle members 48 may be supported by modified supporting members, which include the structure of a supporting means 52, above described, with an extension of the head portion at one end thereof provided with a suitably shaped opening therein to receive the baflle member 48.

The bafile means in the above described embodiment of FIGS. l-4, inclusive, insures substantially complete and uniform coverage of the outer surfaces of the plates 16 with liquor sprayed by the nozzles 41, 42. The sprays from such nozzles, as shown in FIG. 1, overlap to some extent and travel downwardly at their borders at a moderate angle with respect to the vertical. By far the predominant part of such spray is directly intercepted by the first bafile members, which include the upper edges of the joints 46 and the outer surfaces of the upper angularly disposed portions 51 of the plates 16, and by the upper angularly disposed surfaces of the second baffle members 47, 48. Only that small portion of the spray which passes between the boundary paths 59 and 60, shown in FIG. 4, can possibly travel directly from a nozzle through the gap between the outer surface of plate portion 51 and the lower edge 50 of a bafiie 47. This, however, constitutes a relatively insignificant portion of the total spray delivered by the nozzles. Further, since the nozzles are symmetically disposed above the plate system and the same conditions for travel of spray through the aforesaid gaps exist for all plates, and for spray which travels in paths inclined in both directions with respect to the vertical, the total liquid falling upon each of the plates 16 and thus forming a downwardly falling film thereon is substantially equal.

In FIG. 5 there is shown a second embodiment of liquid distributing system in accordance with the invention, such system precluding the direct impingement of any liquor from the spray means directly upon the outer surface of the main vertical portion of any of the plates 16. The embodiment of FIG. 5 difiers from that of FIGS. 1-4, inclusive, in that the second baffie members are made with a somewhat larger apex angle than those of FIGS. 1-4, inclusive. Thus the lower edges of such second baffle members lie further apart than those of the first described embodiment. The second bafile members are so related to the first baflle members and to the spray nozzle or nozzles 41 employed that under no conditions can spray travel directly from the nozzle 41 through any gap presented between the outer surface of a plate 16 and its first baffie member-providing upper end and the confronting lower edge of the respective second baffie member. As an alternative to the construction of FIG. 5, generally the same result may be obtained by modifying the embodiment of FIG. 4 to lengthen the sides of baffie members 47, thereby to bring the lower edges 50 of such sides closer to the portions 51 of the respective plates 16 which they confront.

Since the embodiment of FIG. 5 is generally the same in structure as that of FIGS. l-4, inclusive, the parts of the baffle means, generally designated 62, shown in FIG. 5 are designated by the same reference characters as those employed in FIGS. l-4, inclusive, but with added primes. In the embodiment of FIG. 5, as above noted, a greater apex angle between the sides of the bafiles 47 is employed than in FIGS. 1-4, inclusive. This permits a closer approach of the lower edges 50' of the second baflie members to the surfaces of the plates 16 forming the first bafiie means, such lower edges overlapping the first bafile members.

As shown in FIG. 5, the spray progressing from a nozzle 41 between the same boundary paths 59, 60 as those shown in FIG. 4 will strike, respectively, the first bafiie members, that is, the upper edge of the plate 16' at the joint 46' or the upper edge of the portion 51' of the plate, or the lower edge portion of the second battle members. As in the embodiment of FIGS. 1-4, inclusive, this is only a small :part of the total spray delivered by the nozzle or nozzles, the remainder being directly intercepted by the bafiie members, as in the system of FIG. 4.

Thus the direct impingement of the sprayed liquor upon the outer surface of the main vertical portions of plates 16, which, as above explained, occurs to a minor extent in the embodiment of FIGS. l-4, inclusive, is completely eliminated in the liquor distribution system of FIG. 5.

Although a limited number of embodiments of the invention have been illustrated in the accompanying drawings and described in the foregoing specification, it is to be especially understood that various changes, such as in the relative dimensions of the parts, materials used, and the like, as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention, as will now be apparent to those skilled in the art.

What is claimed is:

1. In a falling film heat exchanger having a plurality of generally vertically disposed spaced plates forming sets of alternate channels isolated from each other, a first set of said channels being adapted to receive liquid to be heated, a second interdigitated set of said channels being adapted to receive a heating fluid, the improved means for distributing liquid to be heated over the exterior heating surfaces of the heat exchanger plates in the first channels, which comprises an upwardly convex first bafiie member in the form of a hood disposed at the upper end of each of the second channels and extending along the upper edges of the heat exchanger plates, the lower edges of the bafile members being at least substantially coextensive with the upper edges of the main extents of the heating surfaces of the heat exchanger plates, a liquid conducting means having at least one liquid discharging opening therethrough disposed centrally above an area of the plates at the top thereof, and second battle members interposed between successive first bafile members, means supporting the second bafile members with respect to the first bafile members, said first and second bafile members intercepting substantially all of the liquid directly discharged from the opening and distributing it to fall substantially uniformly onto the bafile members in said area, whereby the thus intercepted liquid flows down the sides of the baflle members to form substantially uniform films flowing down the entire area of the heating surfaces of the heat exchanger plates.

2. A heat exchanger as claimed in claim 1, where the upper edges of the first and second baffle members lie substantially in the same horizontal plane.

3. A heat exchanger as claimed in claim 2, wherein the second bafiie members are offset laterally with respect to the first recited baffie members and are disposed in a generally horizontal row, each of the second bafile members having its opposite lower edges spaced horizontally sufiiciently at least to be tangent to the plane of the outer surfaces of the plates which form the first channels.

4. A heat exchanger as claimed in claim 3, wherein the opposite lower edges of each of the second baflle members overlap the respective first batfie members which they confront.

5. A heat exchanger as claimed in claim 3, wherein the first and second bafiie members are generally of laterally symmetrical inverted V-shape in vertical transverse section, and the second bafile members are disposed centrally between successive first baflie members.

6. A heat exchanger as claimed in claim 3, wherein said bafile supporting means comprises means supporting the second bafile members upon the first recited bafiie members.

7. A heat exchanger as claimed in claim 6, wherein said supporting means for the second bafiie members comprises at least two supporting members for each of the second bafiie members, said supporting members being spaced longitudinally of the batfie members, each of said supporting members having a main generally horizontally extending head portion spanning between and being supported upon two successive first bafile members, and

means on said supporting members for supporting the said second bafiie members, the lower edges of the head portions of the supporting members being notched at longitudinally spaced zones to receive the upper edges of successive fi-rst baffle members in respective ones of said notches.

8. A heat exchanger as claimed in claim 7, wherein the head portion of said supporting means comprises a lower portion which is disposed within the upper end of a first channel, the said lower portion having a passage therein through which a second bafile member extends, the portions of the supporting members below the second bafile members substantially spanning the first channels, whereby to act with said notches to center the second bafile members with respect to the first channels.

References Cited UNITED STATES PATENTS Barnsdale 34170 X Ehrman 165115 Kleist 165-115 Kennedy 34-170 Bertetti 202-236 Eckstrom 159-43 Hammer et a1. 202236 Great Britain.

NORMAN YUDKOFP, Primary Examiner.

F. SOFER, Assistant Examiner. 

1. IN A FALLING FILM HEAT EXCHANGER HAVING A PLURALITY OF GENERALLY VERTICALLY DISPOSED SPACED PLATES FORMING SETS OF ALTERNATE CHANNELS ISOLATED FROM EACH OTHER, A FIRST SET OF SAID CHANNELS BEING ADAPTED TO RECEIVE LIQUID TO BE HEATED, A SECOND INTERDIGITATED SET OF SAID CHANNELS BEING ADAPTED TO RECEIVE A HEATING FLUID, THE IMPROVED MEANS FOR DISTRIBUTING LIQUID TO BE HEATED OVER THE EXTERIOR HEATING SURFACES OF THE HEAT EXCHANGER PLATES IN THE FIRST CHANNELS, WHICH COMPRISES AN UPWARDLY CONVEX FIRST BAFFLE MEMBER IN THE FORM OF A HOOD DISPOSED AT THE UPPER END OF EACH OF THE SECOND CHANNELS AND EXTENDING ALONG THE UPPER EDGES OF THE HEAT EXCHANGER PLATES, THE LOWER EDGES OF THE BAFFLE MEMBERS BEING AT LEAST SUBSTANTIALLY COEXTENSIVE WITH THE UPPER EDGES OF THE MAIN EXTENTS OF THE HEATING SURFACES OF THE HEAT EXCHANGER PLATES, A LIQUID CONDUCTING MEANS HAVING AT LEAST ONE LIQUID DISCHARGING OPENING THERETHROUGH DISPOSED CENTRALLY ABOVE AN AREA OF THE PLATES AT THE TOP THEREOF, AND SECOND BAFFLE MEMBERS INTERPOSED BETWEEN SUCCESSIVE FIRST BAFFLE MEMBERS, MEANS SUPPORTING THE SECOND BAFFLE MEMBERS WITH RESPECT TO THE FIRST BAFFLE MEMBERS, SAID FIRST AND SECOND BAFFLE MEMBERS INTERCEPTING SUBSTANTIALLY ALL OF THE LIQUID DIRECTLY DISCHARGED FROM THE OPENING AND DISTRIBUTING IT TO FALL SUBSTANTIALLY UNIFORMLY ONTO THE BAFFLE MEMBERS IN 